1. Field of the Invention
The present invention relates to a gloss control apparatus and a gloss control method of controlling glossiness of an image recording surface of a heat-sensitive recording medium that develops at least one color in response to an application of thermal energy.
2. Description of the Related Art
Various methods have been developed for recording information such as texts and images, including electrophotography, ink-jet printing and thermal printing. The thermal printing utilizes a heat-sensitive recording medium made of a base material such as paper or synthetic paper to which a coupler or a developer is applied. Thermal energy is applied to the medium by means of a thermal head and the like so that the medium develops a color. An image is thereby recorded on the medium. The thermal printing has advantages in that no development is required as for photography, the density of a color is high and a high-contrast image is obtained and so on. The further advantage is that thermal printing is implemented with a recording apparatus of simple configuration at a low cost. The thermal printing has been therefore widely used in the fields of black-and-white facsimiles, printers and so on.
Although heat-sensitive recording media for black-and-white image printing have been mainly used for the thermal printing, media has been further developed for multicolor image printing including full-color printing. Such a heat-sensitive recording medium for multicolor printing includes a plurality of layers that develop colors different from each other. For example, the medium is made up of a base material to a side of which three color developing layers are stacked. The layers develop a cyan, a magenta and a yellow, respectively. The layers develop colors in response to thermal energy belonging to the different energy ranges. The upper layer responds to higher thermal energy for developing a color, that is, the thermal energy for developing a color increases in the order of the yellow layer, the magenta layer and the cyan layer, for example. The density of developed color increases with an increase in thermal energy within the range of energy for developing each color.
Through the use of a heat-sensitive recording medium for multicolor printing as described above, a long-life multicolor image is obtained, having excellent hues and color separation that are difficult to obtain with prior-art techniques. Another excellent effect is that an image obtained may be turned to a transmission image or a reflection image.
In an image recording method utilizing such a heat-sensitive recording medium, thermal energy to applied is varied depending on an image to record. It is known that a difference in glossiness results on an image recording surface of the medium depending on thermal energy applied. In particular, there is a great difference between part where thermal energy is applied and the other part, that is, between part where an image is actually recorded and part where no image is recorded. Glossiness may vary in part where an image is recorded, too, from place to place, since applied thermal energy varies depending on differences in density and color. In the image recording method utilizing a heat-sensitive recording medium as thus described, uneven glossiness results all over the image recording surface after image recording. Reproducibility of the image is thereby affected. It is therefore desirable to overcome such uneven glossiness.
Techniques for improving such uneven glossiness of a heat-sensitive recording medium are disclosed in Japanese Patent Application Laid-open Nos. 5-24245 (1993) and 6-218968 (1994), for example. In the former one, a technique is disclosed for applying the highest of thermal energy applied to a color developing layer on which image recording is already performed to at least part where the color density is zero. The difference in glossiness between the part where the image is actually recorded and the part where no image is recorded is thereby reduced so that even glossiness is achieved. In the latter one, a technique is disclosed for applying heat and pressure to a heat-sensitive medium by a heat roller after image recording on the medium is completed. The difference in glossiness between the part where the color density is high (where high thermal energy is applied) and the part where the color density is low (where low thermal energy is applied) is thereby reduced so that even glossiness is achieved. As thus described, the techniques for mainly improving uneven glossiness of the heat-sensitive recording medium are disclosed in those publications.
According to the techniques, however, glossiness whose evenness has been achieved is automatically determined by the setting of the apparatus. It is not always possible to achieve glossiness as the user desires. For example, although the foregoing related-art techniques achieve even glossiness, whether glossiness improves or not is not disclosed. In some cases, even glossiness of worse quality may be obtained. In general, the user does not need such evenness that deteriorates glossiness but prefers an improvement in glossiness as well as evenness.
In the related-art techniques described above, it is difficult to precisely control thermal energy applied for achieving even glossiness since a heat roller is used as a heat application means. For example, thermal energy more than required may be applied. Achieving precisely even glossiness is thus affected. Since no specific thermal energy necessary and sufficient for achieving even glossiness is disclosed, power more than required may be consumed.